1. Field of the Invention
This invention relates to a durable laminated organic photosentive material which has a charge producing layer and a charge transporting layer formed on an electroconductive support.
2. Description of the Prior Art
A composite or laminated type organic photosensitive material has been developed and put to practical use in recent years. This type of organic photosensitive material is disclosed in, for example, Japanese Patent Publications Nos. 42380/1980 and 34099/1985. It comprises an electroconductive support, a charge producing layer formed on the support and a charge transporting layer formed on the charge producing layer. For instance, such a composite photosensitive material has an electroconductive support of aluminum layer, a charge producing layer formed on the aluminum layer, and a charge transporting layer formed on the charge producing layer.
The charge transporting layer is formed by, for example, preparing a dispersion of a charge transporting substance together with an organic solvent, a binder resin and, if necessary a plasticizer, applying the dispersion onto the support, and drying to a thin film. The charge producing layer is formed by, for example, dissolving a charge producing substance in an organic solvent together with a binder resin and, if required, a plasticizer, applying the solution onto the charge transporting layer, and drying to a thin film.
There are already known a variety of charge producing substances including phthalocyanine compounds, as disclosed in Japanese Patent Laid-Open No. 166959/1984. A number of charge transporting substances are slso already known, and among which is a bistyryl compound represented by the formula ##STR2## as disclosed in Japanese Patent Laid-open No. 30255/1987.
The laminated organic photosentive material which contains the above mentioned bistyryl compound as a charge transporting substance has an advantage that it is readily charged, however, there is an undesirable tendency that cracks are generated on the surface of the charge transporting layer which contains the bistyryl compound when the laminated organic photosentive material is used over a long period of time. Namely, the photosentive material does not stand long term use and hence is non-durable.